This project is concerned with biochemical and molecular aspects of hormone action during fetal development. Fetal liver is used as a cellular model for analyzing the mechanism of glucocorticoid hormone action. the glucocorticoid receptor is purified by DNA-affinity chromatography, and anti-receptor antibodies are prepared for use in determining the chemical structure and biochemical function of the receptor. The role of glucocorticoids in cntrolling the development of carbohydrate metabolism in fetal liver is studied in utero and in vitro using a chemically defined organ culture system. The fetal liver organ culture system is also used to study the synthesis of insulin-like growth factors (sommatomedins) at various stages of fetal development, and the synthesis of major secretory proteins (alpha-fetoprotein and albumin).